Conventionally, resin sealing has prevailed in the field of element sealing for electronic component devices such as transistors, IC etc., from the viewpoint of productivity, costs, etc., and epoxy resin compositions are widely used. This is because the epoxy resin is well-balanced in characteristics such as workability, formability, electrical characteristics, moisture resistance, heat resistance, mechanical characteristics, adhesiveness to an insert material, etc. In semiconductor devices having bare chips mounted thereon, such as COB (Chip on Board), COG (Chip on Glass), TCP (Tape Carrier Package) etc., liquid resin compositions for electronic components are widely used as sealing materials. In a semiconductor device (flip chip) having a semiconductor element bump-bonded directly onto an interconnection substrate, a liquid resin composition for electronic components is used as an underfill agent.
The semiconductor device has narrow wiring width and a narrow pitch between wirings, and some of the state-of-the-art flip chip semiconductor devices have a pitch width of 50 μm or less. A voltage is applied across narrowly pitched electrodes of these semiconductor devices, and ion migration becomes a major issue. Particularly at high temperature under high humidity, migration easily occurs to cause defects in the semiconductor device. As a typical semiconductor device with thinner wirings and narrower pitches, there is COF (Chip on Film), and particularly migration resistance has become important in the field of COF. Conventionally, it is known that reduction of impurities in liquid resin compositions for electronic components is effective in improving migration, but it has become impossible to improve migration by merely attaining higher purity.
Curing of a liquid sealing epoxy resin composition needs heating at high temperature for a long time, and in recent years, there is an increasing demand for rapid-curing liquid sealing epoxy resin compositions aimed at improving productivity. For example, a liquid sealing epoxy resin composition comprising (A) an epoxy resin and (B) a curing agent as essential components, wherein the curing agent (B) comprises an allyl group-containing phenol resin, and the surface of the composition after curing has a reflectance of 10% or less (see JP-A 2002-194066).